Configuring rootDir and outDir

rootDir controls the common directory structure for emitted files; outDir tells TypeScript where to place generated output. rootDir does not decide which files are included in the project. Use include/exclude or files for input selection and keep generated output away from source folders.

The displayed mapping is a model for a typical src/main.ts file. The actual compiler performs the mapping when tsconfig.json sets rootDir and outDir.

rootDir does not exclude files outside the directory from the compilation inputs; it constrains their emitted layout.

Save as configuring-rootdir-outdir.ts. The following program passed strict TypeScript compilation, and the displayed output was captured by executing its emitted JavaScript with Node.js 22.16.0.

TypeScript source

type BuildPaths = { rootDir: string; outDir: string };
const paths: BuildPaths = { rootDir: "src", outDir: "dist" };
console.log(`${paths.rootDir}/main.ts -> ${paths.outDir}/main.js`);

Verified output

src/main.ts -> dist/main.js

Compile: npx tsc --strict --target es2022 --module commonjs configuring-rootdir-outdir.ts; run: node configuring-rootdir-outdir.js. For Node.js API examples, install @types/node first. For browser projects, use the browser-specific instructions below.

The example demonstrates the code-level behavior; the related configuration or test commands are shown separately when needed.

The displayed mapping is a model for a typical src/main.ts file. The actual compiler performs the mapping when tsconfig.json sets rootDir and outDir.

Predict what changes if you alter one input. Then run the code to compare your reasoning with the real output.

Practical project lab: These are real configuration and source-file examples, not a TypeScript object that merely describes settings. Place the files at the named paths relative to one project directory.

tsconfig.json

{"compilerOptions":{"target":"ES2022","module":"CommonJS","strict":true,"rootDir":"src","outDir":"dist"},"include":["src/**/*.ts"]}

src/main.ts

console.log("Build layout");

Commands

npx tsc -p .
node dist/main.js

Check generated dist/main.js and keep outputs out of src.

This local compiler or test-runner mini-project was validated in addition to the primary program.

rootDir does not exclude files outside the directory from the compilation inputs; it constrains their emitted layout.

Identify whether the failure is a type-checking issue, a configuration issue, or a runtime behavior issue before choosing a fix.

Put main.ts in src/ and set outDir to dist/. Compile and inspect the generated folder.

Write down your expected result first. For configuration examples, compare compiler output and diagnostics; for test examples, make the assertion fail deliberately to verify that the tool reports it.

For the exact current options and platform behavior, consult the official documentation. These examples were verified using the tool versions described above.

rootDir controls the common directory structure for emitted files; outDir tells TypeScript where to place generated output.

Run the primary example, then complete the practice task or environment-specific lab.